It basically describes what GoogleBot is able to render and what it is not able to render. It reads:

Googlebot uses a web rendering service (WRS) that is based on Chrome 41 (M41). Generally, WRS supports the same web platform features and capabilities that the Chrome version it uses - for a full list refer to chromestatus.com, or use the compare function on caniuse.com.

However, there are a few exceptions and differences that you should keep in mind. The following features and APIs are explicitly disabled or limited in the WRS: